Secondary-stage throttle control for a multistage carburetor



June 1958 H. A. CARLSON ETAL SECONDARY-STAGE THROTTLE CONTROL FOR A MULTL-STAGE CARBURETOR 2 Sheets-Sheet 1 Filed April 5, 1956 INVENTORS HARQLD A. CARLSON QLIN J. EICKMANN v flMW ATTORNEY June 10, 1958 H. A. cARLsoN ETAL 2,338,293

SECONDARY-STAGE THROTTLE CONTROL FOR A MULTI-STAGE CARBURETOR Filed April 5. 1956 2 Sheets-Sheet 2 a [so 1 /0 37 INVENTORS HAROLD A.CARLSON OLIN, J. EICKMANN ATTORNEY 1 2,838,293 A Patented June 10,- 1958 SECONDARY-STAGE THROTTLE CONTROL FOR A MULTISTAGE CARBURETOR Application April 5, 1956, Serial No. 576,370

Claims. (Cl. 26123) This invention relates to multi-stage carburetors of the type in which both primary and secondary stages are controlled by separate but interconnected and manually operated throttle valves, and more specifically to a mechanism for modifying the rate of opening of the secondary throttle during full opening of the primary throttle.

According to the instant invention, the carburetor has a manually operated primary throttle and a secondary throttle which is unbalanced to be closed by suction. A resilient lost-motion connection between the primary and secondary throttles applies a force tending to open the secondary throttle as the primary throttle is manually moved toward wide-open position. More specifically, the opening force is applied to the secondary throttle by a spring during the final range of opening movement of the primary throttle, and is opposed by suction acting directly on the valve. A damping device is connected to the secondary throttle to retard its rate of opening. As the primary is closed, spring force decreases and'suction closes the secondary.

It will be readily understood that initial opening of the secondary throttle will be retarded in a degree dependent upon the differential of pressure thereacross, so that, when the manifold suction is high, sudden action is avoided and engine response will be smooth under these circumstances. When the opposite suction conditions exist, the action of the clamping device will control the rate of opening movement of the secondary throttle.

It is a further feature of this invention to provide a hydraulic damping device in the form of an accelerator pump having its discharge connected preferably with the secondary stage mixture conduits. Since the damping device is operated directly from the secondary stage throttle, an immediate delivery of fuel results from secondary throttle operation, which will avoid any objectionable change in the mixture ratio, which sometimes occurs due to the lag in the fuel delivery from the secondary stage main fuel nozzle.

Other objects and advantages of the invention will become apparent from the detailed description which follows, taken with the accompanying drawings, in which:

Fig. l is a view, in elevation, of one side of the carburetor.

Fig. 2 is a view, in section, through the primary and secondary barrels of the carburetor shown in Fig. 1.

Fig. 3 is a fragmentary view illustrating the position of the parts in the throttle linkage during the initial opening movement of the primary throttles.

Fig. 4 is a fragmentary view of the same side of the carburetor as Fig. l, illustrating the position of the parts of the throttle linkage with both primary and secondary throttles wide open.

Fig. 5 is a side elevation of the opposite side of the carburetor shown in Fig. l.

The invention is illustrated as applied to a multi-barrel, multi-stage carburetor of the type commonly referred to 2 are generally shown in many patents; for example, the patent to Carlson et al., 2,715,522 of August 16, 1955. Since this invention is primarily concerned with a mechanism for controlling the operation of the secondary throttles, details of the fuel system will not be described, since they form no part of the present invention.

Fig. 1 shows a carburetor having an air horn section 1 constructed integrally with a float bowl cover 2 which is, in turn, secured to the fuel bowl section 3 by the usual screws 4. A mounting flange 5 is formed integrally with the fuel bowl section 3, and may be provided with the usual holes (not shown) for securing the carburetor in place on the intake manifold of an engine.

Within the carburetor are the usual pair of primary mixture conduits 7 and the usual pair of secondary mixture conduits 8, both of which are indicated by dotted lines in Fig. 1. As shown in Fig. 2, the outlets of the primary mixture conduits 7 are separately controlled by throttle 9 mounted on a throttle shaft 10. Since both mixture conduits are identical, only one is illustrated and described here. Above the throttle 9 is a main venturi 11 within which is mounted a primary venturi 12 containing the fuel nozzle 13. In this carburetor, the main fuel nozzle 13 and primary venturi 12 are formed integrally with a mounting block 14 secured in place within a suitable recess formed in the wall of the primary mixture conduit 7.

The entrance of both primary mixture conduits 7 is controlled by a single choke valve 16 mounted on a choke valve shaft 17. This valve is controlled by suitable linkage from an automatic temperature and suction responsive mechanism 20 mounted on the side of the carburetor, all as shown in Fig. 1. The choke housing 20 contains the automatic choke control mechanism, which may be of any suitable type, but is preferably that shown in the patent to Coffey 2,325,372 of July 27, 1943. A control arm 21 actuated by this mechanism is connected through link 22 and levers 23 and 24 on a countershaft 25 with a link 26 extending to a bracket 27 integral with the choke valve 16. I

Fig. 2 of the drawing shows one of a pair of secondary mixture conduits 8, and, since both are identical, an explanation of one will serve for all. Journaled in the mixture conduit is a secondary throttle shaft 30 which is slightly offset with respect to the center line of the mixture conduit. This amount of offset or eccentricity is illustrated here between the center line X-X of the secondary throttle shaft 30 and the center line YY of the secondary mixture conduit 8. Throttle valve 31 is secured to the secondary throttle shaft in a manner so that it becomes an unbalanced valve closed by engine suction. Hereafter, the valve is concisely described as unbalanced to close. This terminology is applied to specifically describe a valve mounted in this manner.

Within the mixture conduit 8 is a main venturi 32, and within the main venturi 32 is a primary venturi 33 hav ing a secondary main fuel nozzle 34. The fuel nozzle and primary venturi are formed as a unit supported by a block 35 seated in a recess in the side of the mixture conduit 8.

As shown in Fig. 2, the primary mixture conduits 7 are each provided with idle ports 37 and 38 adjacent the edge of the throttle 9. A fuel passage 39 extends to a cross passage 40 interconnecting the idle systems with the main fuel supply to the primary fuel nozzles 13, all in a well known manner. Although no idle system is shown on the secondary side, this may be provided if desired. A fuel nozzle 41 connects by way of a passage 42 with an accelerating pump (not shown). The plunger 43 for actuating this pump is shown in Fig. 5,

as a four-barrel. The details of this'type of carburetor together with its operatinglinkage '44 and 45 connecting it with the lever 46 secured to the primary throttle shaft Within the secondary mixture conduit is a similar fuel nozzle 47 connected by way of a passage 48 containing a check valve 49 with a cross passage 50 leading to the accelerating pump 51 located within the fuel bowl of the carburetor. The primary throttle lever 53, shown in Fig. 5, has a hole 54 for connection with the control rod from the accelerating pedal. Its opposite end'mounts an adjusting screw 55 in a threaded boss 56, which contacts the active face of the fast idle cam 57. A stud 58 rotata-bly mounts the fast idle cam, which has an op posite arm 59 connected by a link 60 with arm 61 on the choke eountershaft 25. Also mounted on the stud 58 is a weighted lever 63 formed with the abutment 64 and an outstanding lug 65. Shoulder 64, in turn, engages With a latch 66 secured to secondary throttle shaft 30 for holding the secondary throttle closed.

Lever 53 also carries a lug 70 positioned for engagement with an idle adjusting screw 69 on the body of the carburetor 3. The end of the lever 53 has an inturned lug 72, which is adapted to engage with the face of lever 59 as the primary throttles are fully opened to open the choke.

The mechanism for operating the secondary throttle shaft 30 from the primary throttle shaft 10 is most clearly shown in Figs. 1, 3 and 4. As shown in these views, the primary throttle shaft carries a fixed member formed with three lugs or arms 76, 77 and 78. Arm

76 carries an inturned lug 79 engaging with the face 80 on lever 81 rotatably mounted on the throttle shaft 10. A link 82 connects lever 81- with a short lever 84 fixed to the secondary throttle shaft 39. Arms 77 and 78 each have, in turn, end lugs 86 and 87, each of which engages with an end 90 and 91 of a torsion spring. A link 94 connects arm 81 with a pivoted arm 95 having a finger 96 engaging the plunger 97 of the accelerating pump 51.

Operation The arm 53 in Fig. 5 constitutes a means for controlling the position of the primary throttles 9 within the mixture conduits 7, and it, in turn, is provided with adjustments 55 and 69 for limiting the closed position of the throttles 9.

The automatic choke mechanism 20 controls the position of the fast idle cam 57 through its connection with the countershaft 25, and, as the choke valve opens in response to the increase in temperature of the engine, arm 59 will rotate into engagement with lug 65, releasing the shoulder 64 from the arm 66 to unlateh the secondary throttles for operation. The operation of the primary throttles by the lever 53 will, in turn, depress the plunger 43 of the primary accelerating pump to inject fuel into the primary mixture conduits through the nozzles 41.

After the latch 64, 66 is released, the mechanism interconnecting the primary and secondary throttle shafts 10 and 30 becomes operative. Since it can be readily seen that, so long as the secondary throttles remain locked, opening movement of the primary throttles merely compresses the spring arm 91 after it engages the lug 99 on the lever 81. Full opening movement of the primary throttles, even when the secondaries are latched, however, performs the unloading function by the engagement of lug 72 with the arm 59 to force the weighted lever 63 to unlateh.

As shown in Figs. 1, 3 and 4, when the primary throttles are closed, lug 79 engages the face of shoulder 80 on the lever 81, rotating this lever to the position shown in Fig. 1, in which it holds the secondary throttles 31 closed. After the primary throttles 9 have moved to the position shown in Fig. 3, one arm 91 of the torsion spring engages the lug 99, and further movement of the primary throttles in the opening direction applies. aresilient force to the secondary throttle shaft 30, tending.

4 to open the secondary throttles against the force of suction; It will be readily recognized, therefore, that the opening sequence of the two pairs of throttles 9 and 31 will depend upon the degree of unbalance of the secondary throttles and the suction force acting thereon compared with the opening force exerted by the spring arm 91. At the same time, the opening rate of movement is affected by the-hydraulic damping action imposed by the accelerating pump 51 after the secondary throttles have opened,

The primary throttles may open beyond the position shown in Fig. 3 before the initial opening action of the secondary throttles 31 occurs because the gearing between the throttles is not a positive kind, and spring 9--91 may be compressed some before the suction force on the secondary is'..overcome.

As soon as the secondary throttles begin to open, the damping device, which is an accelerating pump 51, will discharge some fuel through the fuel nozzles 47, which will compensate for any lag in the operation of main fuel nozzle 34. By proper calibration of the spring force 91, and a restriction 49a in the accelerating pump circuit conduit 48, a controlled rate of opening is obtained for the secondary throttles 31. Generally speaking, the hydraulic damping action imposed by the accelerating pump 51 will be a constant one throughout the opening movement of the secondary throttles, and dependent entirely upon the size of the restriction 49a in the discharge line. The effect of spring 51', however, should not be neglected, since it can impose an increasing force resisting throttle movement.

A structure has been described which will fulfill all of the objects of the present invention, but it is contemplated that other modifications will occur to those skilled in the art which come within the scope of the appended claims.

We claim:

1. In a multi-stage carburetor, the combination of primary and secondary mixture conduits, a manually controlled primary throttle in said primary mixture conduit, a secondary throttle in said secondary mixture conduit unbalanced to close by engine suction, resilient means between said throttles operative to open said secondary throttle responsive to opening movement of said primary throttle, and yielding means resisting the action of said resilient means.

2. The combination defined in claim 1, in which said yielding means comprises an accelerating pump in said carburetor, a fuel passage from said pump to said secondary mixture conduit, and a fuel metering restriction in said passage.

3. In a multi-stage carburetor, a combination of primary and secondary mixture conduits, a manually controlled primary throttle in said primary mixture conduit, a. secondary throttle unbalanced to close said secondary mixture conduit by the action of suction thereon, linkage means connected to said secondary throttle and movable to open said secondary throttle, resilient means connected to the primary throttle and movable therewith to actuate said linkage means to urge said secondary throttle open, means to move said resilient means into engagement with said linkage means to resiliently urge said secondary throttle open in response to opening movement of said primary throttle, and yielding means resisting the action of said resilient means for controlling the rate of opening of said secondary throttle.

4. In a multi-stage carburetor, the combination of primary and secondary mixture conduits, a manually con trolled primary throttle in said primary mixture conduit, a secondary throttle mounted in said secondary mixture conduit, resilient means between said throttles operative to open said secondary throttle responsive to opening movement of said primary throttle, pump means yieldingly resisting the action of said resilient means, means for supplying fuel to said pump means, and a connection between said pump means and said secondary mixture conduit for discharging fuel thereto during opening movement of said secondary throttle.

5. In a multi-stage carburetor, a combination of primary and secondary mixture conduits, a manually con-- trolled primary throttle in said primary mixture conduit, a secondary throttle unbalanced to close said secondary mixture conduit by the action of suction thereon, linkage means connected to said secondary throttle and-movable to open said secondary throttle, resilient means con nected to the primary throttle and movable therewith to actuate said linkage means to urge said secondary throttle open, means to move said resilient means into engagement with said linkage means to resiliently urge said secondary throttle open in response to opening movement of said primary throttle, yielding means resisting the action of said resilient means for controlling the rate I ment of said actuating means.

References Cited in the file of this patent UNITED STATES PATENTS 2,193,533 Kishline et al. Mar. 12, 1940 2,254,834 Betry Sept. 2, 1941 2,363,153 Shipman Nov. 2, 1944 2,609,807 Winkler Sept. 9, 1952 2,635,863 Olson Apr. 21, 1953 2,681,213 Gordon June 15, 1954 2,732,191 Smitley Jan. 24, 1956 

